1. Field of the Invention
The present invention relates to a method for compensating offset of current sensor, and more particularly to a method for compensating offset of current sensor configured to be used for a current sensor for detecting a current flowing in a motor of a driving power source for hybrid electric vehicles (HEVs) and electric vehicles (EVs).
2. Discussion of the Related Art
The information disclosed in this Discussion of the Related Art section is only for enhancement of understanding of the general background of the present invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
In recent years, with the aim of reducing CO2 discharge in an attempt to prevent global warming and air pollution, hybrid electric vehicles (HEVs) and electric vehicles (EVs) have gained great attention as eco-friendly vehicles.
HEVs are mounted with a motor driven by electricity, in addition to a conventional engine as power supply source. To be more specific, a power supply system of an HEV includes a main battery (high voltage battery) supplying a driving power to a driving motor, a BMS (Battery Management System), a sub-battery (low voltage battery) providing a driving power to other vehicular electronic equipment and a host of electric devices.
An inverter may act as an intermediary between battery and electric motor. That is, an inverter converts a high DC (direct current) voltage generated by the main battery (high voltage battery) to an AC (alternating current) signal to control a motor. That is, the HEVs are mounted with as power supply sources a DC power source, an inverter and a motor driven by the inverter.
In the HEVs or EVs, an MCU (Motor Control Unit) precisely controls the motor based on a detection value of output torque of a motor, and a detection value of motor current flowing in the motor. Meanwhile, a motor current detected by a current sensor has a predetermined difference from a current actually flowing in the motor, which is called an offset of the current sensor. The offset of the current sensor is a very small amount of current necessary for operating the current sensor, and a motor current detected by the current sensor actually includes a current flowing in the motor and the offset, such that the offset is compensated by the motor current detected by the current sensor.
If a motor current that has not compensated the offset is provided to the MCU, a pulsation of a motor output torque may be caused by an error between detected current by the current sensor and actual current flowing in the motor, whereby an entire system may be destabilized. Generally, as a measure to combat this phenomenon, an offset is predetermined at an initial driving of a motor, and an offset is compensated to the current detected from the current sensor.
Meanwhile, the offset of the current sensor is generally changed by an external noise, aging, ambient temperature change and deterioration of the current sensor. Thus, a constant compensation of offset at the initial driving may inevitably cause generation of an error between a motor current detected by the current sensor and an actual motor current, leading to generation of pulsation and impossibility of stable motor control. Furthermore, if a mechanical resonance point of an entire system (EV) and a pulsating frequency of an output torque are synchronized, it is natural that the entire system is disadvantageously destabilized over time.